giant waves in the magnetosphere

As you can see, the waves were recorded passing over a large area of Scandinavia. Notice too that the waves aren't quite the same at the different observatories.

Still longer period waves are found in the outer magnetosphere. We think these are a direct result of the solar wind flowing along the boundaries of the magnetosphere without actually penetrating it. This is a bit like the wind blowing across the sea and causing waves.

Since we know how far apart the recording stations are, we can use this difference to work out how fast the wave is travelling.